The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that the referenced prior art forms part of the common general knowledge in Australia.
Conventional GPOs include a socket and switch sub-assembly including a polymer, insulating body portion supporting active, neutral and earth inner female prong contacts disposed toward the eventual front of the GPO, and corresponding electrical screw terminals disposed toward the eventual rear of the GPO. The sub-assembly is secured to the back of a mounting plate which has insulative prong apertures therethrough that are spaced sufficiently from the female conductors for safety. The prong apertures have a tapered lead-in for some or all of the prongs to precisely align the prongs with the contacts. The spacing is essentially an air gap, with the mounting plate sometimes supported back to the socket assembly by, for example, extended prong guides about the prong apertures, bridging the air gap.
The mounting plate is secured to a wall or other surface by screws disposed to each side of the sub-assembly. The wall or surface is generally cut away to receive part of the sub-assembly to ensure a low profile for the GPO. The screws may be penetrating fixings to the wall or surface or metal threads engaging a C-clip or wall box or the like. The mounting plate may comprise either a unitary plate having prong apertures and rocker switch windows, or a two-piece mounting plate including a snap-on bezel to conceal the screw fixings.
A disadvantage of the conventional GPO in exterior use is the lack of weatherproofing of, especially, the prong apertures. Water entry represents a source of corrosion of the GPO metal electrical parts as well as an electric shock hazard.
The provision of GPOs for exterior use requires providing the GPO with a degree of weather resistance. By regulation, the power sockets and switches used in wet/damp areas and in outdoor areas require waterproofing in order to prevent fluid, dust particles or third party from getting inside the socket and inner assembly. Conventional weatherproof power sockets or switches are generally surface mounted and accordingly bulky to maintain weatherproof rating. Currently, there is no weatherproof model comparable in profile and presentation to interior GPOs such as the flush mount GPOs described above.
Prior art weatherproof GPOs include bulky devices with significant projection from a wall or other mounting surface of least 72 mm. The large upper surface area of this device collects dust. The projection from wall in use can hamper people's movement. The projection from the surface is as visually unappealing as it is bulky. The socket outlet is located on an underside surface of the device at an angle to prevent contact with rain. The user is required to insert the electrical plug into the socket outlet from beneath, and potentially unsighted where the device is mounted low on the wall or surface.
The entry pin holes of the socket outlet are environmentally protected to a degree but remain open holes, resulting in limited weatherproof rating. Splashing or spraying fluid, dust particles and insect can still get inside the socket. The device does not prevent children from inserting metal objects into the socket.
Another type comprises a weatherproof enclosure box including a hinged door. The weatherproofing aspects are entirely embodied in the enclosure, not in the GPO per se. The hinge door has an external hinge that can be easily broken. The enclosure lid needs to be opened before inserting the electrical plug. In an installation with two power sockets, the aperture of the second socket remains exposed when only one socket is used. In a typical installation of this enclosure, an indoor power point or switch is often used inside the enclosure. An indoor power point or switch has rocker switches that are not sealed resulting in a weatherproofing weak spot. Some designs attach a rubber cover over the power switch using adhesive glue. Over time, the rubber cover becomes loose and loses its weatherproof protection.
In a third embodiment of prior art GPOs, in order to prevent accidental insertion of object into power socket by children, a safety shutter may be employed by some designs. The safety shutter is a mechanical stop that is moved and opened by correct insertion of the plug pins. Upon insertion of the (longer) earth pin, shutters inside the active and neutral apertures are opened. The safety shutter is constructed of hard plastic that it is not waterproof and dustproof. Due to the nature of design, the power sockets have tight aperture and insertion of power plug is difficult.
US Patent Publication US 2008/0081496 discloses a weather resistant electrical outlet cover 10 which is used with a surface-mounted electrical outlet box assembly 12 comprising a housing 14, a duplex, switchless electrical receptacle 16 and a face plate 18. The cover 10 is a single, continuous cover extending to side wall portions 26 of the housing 14. As the electrical receptacle 16 is duplex, there are two protruding receptacle outlet faces 36. The cover 10 accordingly has two corresponding outlet face cover portions 48 that protrude forward of a front surface 10a of the cover 10. The cover 10 is sandwiched between the face plate 18 and the electrical receptacle 16 except over the outlet face cover portions 48. The cover 10 is made of a water-proof, electrically-insulating, resilient material such as silicone rubber. Narrow, self-closing slits 50 are cut into the outlet face cover portions 48 in alignment with prong openings 44 in the receptacle 16. The outlet face cover portions 48 are relatively thin ( 3/32″ or about 2.4 mm) silicone rubber, to minimize the foreshortening of the penetration of the plug prongs into the receptacle 16.
The disadvantages of the arrangement include the tendency of the thin silicone about the self-closing slits to be wobbling and damaged by the act of prong insertion. Further, the cover 10 arrangement is not well suited for use with low profile, flush mounted wall plates. Water likely infiltrates through joint between cover and plate. The need for an external screw to secure the cover on the plate results in a weatherproofing loophole. Ultimately the 2.4 mm thickness of the insulative outlet face cover portions 48 reduces the penetration of the prongs into the female contacts resulting in bad conduction.